Field of the Invention
The present invention relates to a method of producing a suspension board with circuit, and particularly to a method of producing a suspension board with circuit used in a hard disk drive.
Description of the Related Art
A suspension board with circuit including a metal supporting board, an insulating base layer formed thereon, and a conductive pattern such as wires formed thereon has been known. The suspension board with circuit on which a magnetic head is mounted is used in a hard disk drive or the like.
The conductive pattern includes write wires and read wires. Each of the wires has a front end portion connected to the magnetic head and a rear end portion connected to an external board. To reduce noise in signal transmission, the conductive pattern includes the pair of write wires and the pair of read wires. As each of the write wires and the read wires, differential signal wires including a first wire which transmits a first electric signal, and a second wire which transmits a second electric signal in antiphase to the first electric signal are typically used.
In such differential signal wires, a differential impedance is generated so that differential impedance needs to be reduced.
As a countermeasure against the differential impedance, a configuration (interleaved wiring) in which the first and second wires in each of the pair of write wires and the pair of read wires are alternately arranged has been known. In this configuration, it is necessary to allow the first wires to cross the second wires without causing contact therebetween. That is, it is necessary to electrically connect one (first wire) of the wires in one pair to one (first wire) of the wires in the other pair over the other wire (second wire) in each of the pairs.
As an implementation of such a method, Japanese Unexamined Patent No. 2012-114217 discloses a suspension board with circuit in which, on one side and the other side of second wires, respective metal conducting portions are formed to extend through an insulating base layer and connect first wires and a metal supporting board. In the suspension board with circuit, the first wire located on one side is electrically connected to the first wire located on the other side via the metal conducting portion located on one side, the metal supporting board, and the metal conducting portion located on the other side. This allows the first wires to cross the second wires without causing contact therebetween.